1. Field of the Invention
The present invention relates to a digital/analog broadcast receiver that can selectively receive a digital broadcast and an analog broadcast.
2. Description of the Related Art
A period (simultaneous broadcasting period) during which a broadcasting station releases both an analog broadcast and a digital broadcast is necessary for a transition period wherein analog broadcasting is shifted to digital broadcasting. During the simultaneous broadcasting period, the broadcast can be viewed using either an analog broadcast receiver or a digital broadcast receiver. Further, both broadcasts can be viewed by a digital/analog broadcast receiver that can selectively receive a digital broadcast and an analog broadcast.
For the analog broadcasting, one channel (a physical channel) is provided for one frequency band allocated for each broadcasting station. For the digital broadcasting, however, one channel (a physical channel) and multiple channels (virtual channels) obtained by dividing the physical channels are provided for one frequency band allocated for each broadcasting station. Therefore, for digital broadcasting, more programs can be broadcast over a limited frequency band.
For example, for CATV (Cable Television) in Japan, 113 physical channels, each having a frequency bandwidth of 6 MHz, are provided for the frequency band 93 to 767 MHz. In addition, since a maximum of four virtual channels can be provided for one physical channel, a maximum of 452 programs can be broadcast. In order to set up a receiver for the reception of such an enormous number of channels, disclosed in JP-A-2000-115742, for example, is a digital broadcast receiver that automatically fetches and retrieves data and sets up a channel table (data representing the correlation between physical channels and virtual channels). According to the digital broadcast receiver, the manual setting of a channel table is not required during the installation process, and thus the installation can be facilitated.
However, the proposal in JP-A-2000-115742 is available only for digital broadcasting, and simultaneous broadcasting, for transmitting both a digital broadcast and an analog broadcast, is not taken into account. A virtual channel table (hereinafter referred to as a VCT) 70 is defined in ATSC (Advanced TV System Committee) A65-A, in which the digital broadcasting standards for the United States are set forth. A VCT 70 includes both information concerning digital broadcasting and information concerning analog broadcasting. However, when a digital/analog broadcast receiver is employed to designate a carrier frequency described in a VCT 70 and to tune the frequency, the digital/analog broadcast receiver can not receive a broadcast at a frequency that is shifted, even slightly, away from the tuned frequency.